Wound dressings with layers for absorbing body fluids are known in the art. Absorbent layers are provided for the uptake of body fluids, especially wound exudate, so as to enable the wound dressing to keep a constant moist environment over the wound site, and at the same time avoiding maceration of the skin surrounding the wound.
Much effort has been directed to enhancing the rate of uptake and capacity of the wound dressing, in particular the absorbent layer, to uptake body fluids. Absorbent layers in wound dressings have comprised hydrocolloid, super absorbents, foams and synthetic materials which have extensive capacity to absorb body fluids, especially wound exudate.
However, increasing the capacity and rate of fluid uptake within a wound dressing may give rise to problems, both in assuring that the body fluids do not migrate from the wound dressing and in assuring the wound does not dry out.
Hydrocolloid dressings are some of the most efficient and mostly used dressings, being skin-friendly, absorbent and capable of creating moist wound healing conditions. However, when used on some exuding wounds, the absorption rate tends to be too low. The advantages of the hydrocolloid dressing are the ability of creating a moist wound healing environment and acting as a barrier against bacteria.
A frequent problem when treating exuding wounds is maceration. Usually the absorbent part of the dressing is optimised to substantially vertical absorption, so that the skin surrounding the wound is not exposed to the exudate in order to avoid maceration of this healthy, but fragile skin. However, these properties are s limiting the absorption capacity of the dressing to the part of absorbent material being directly over the wound. Barrier cream/skin conditioning paste, such as zinc paste, may be used on the surrounding skin in order to avoid the maceration, but the paste will often inhibit both the adhesive tack of the dressing as well as the ability of absorbing exudate.
Highly exuding wounds are often treated with foams or alginates, which are capable of absorbing high amounts of exudate but requires additional cover dressings, as well as the risk of maceration is high. The retention of foam is low, which may be a problem when used on body parts being exposed to pressure.
A way of overcoming the problems with limited absorption capacity is to create a dressing with high permeability. This is usually done by using a backing layer being more permeable to vapour, but still liquid and bacteria impermeable. Using such a film the absorption capacity will rise when the permeability rises, enhancing the absorption capacity of the dressing. The capacity rises due to evaporation of moisture through the backing layer.
The skin surrounding leg ulcers is often very fragile and thus easily damaged. Wound dressings comprising a direct contact between pressure sensitive adhesives, such as hydrocolloid adhesives or medical acrylate based adhesives, which are often used on commercially available film products, and the skin are not suitable for treatment of such wounds. Traumatic removal of the adhesive dressings with damage to the skin is common, and suggest the use of non-adhesive products.
The skin may be so damaged that exudate trickles from the skin surrounding the wound, being a challenge to most of the well-known dressings. Furthermore, the area of the lower limb may comprise special demands to the flexibility properties of the dressing due to the anatomical complexity of the area combined with the movability of the joints of the ankle and malleolus.
Another important consideration in the treatment of leg ulcers is that the dressing must not give rise to pressure sores. A non-adhesive dressing is usually combined with compression therapy. Thus, a dressing being flat, soft and without sharp edges is preferred.
It is often necessary to treat the fragile skin with ointments or pastes in order to neutralise the impact of the pressure sensitive adhesive on the skin, increasing the risk of leakage on products solely based on pressure sensitive adhesives, as the absorption of the exudate is dramatically reduced when the skin and thus the adhesive area is covered with a lipid containing layer, such as a zinc paste or silicone-products.
Leg ulcers are known to be highly exuding, and may give rise to increased risk of leakage and maceration, if the used wound dressing does not have a sufficient capacity of exudate handling with respect to time and amount. Hydrocolloid products as the above mentioned will often be unsuitable for use in wound healing stages with medium to high exudate level, especially if the skin is covered with a lipid containing products.
International Patent Application No. WO A 98/31402 discloses a wound dressing comprising a perforated wound contacting layer such as a film or a net, a backing layer, and between these two layers is a fibrous absorbent layer. The absorbent layer and the backing layer are combined by heat-lamination. This bandage is absorbent and highly permeable, but may give rise to maceration as the absorbent part may be in contact with the surrounding skin. Leakage may also be a problem.
In International Patent Application No. WO 99/06077 is disclosed a non-adhesive wound dressing which is in the form of an island dressing. The dressing comprises a top film, coated with an adhesive, an absorbent pad of a size smaller than the top layer mounted on the adhesive layer, in order to create an adhesive-covered flange around the absorbent pad, and a non woven layer covering all of the skin contacting surface of the dressing. The permeability of the dressing may however be limited due to the overall adhesive coating as well as maceration may occur along the edges of the absorbent pad, extending further than the wound.
In wound dressings comprising multiple layers including highly permeable films, the different layers of the dressing are often combined by the use of adhesive, usually by coating the backing layer, fully or partly, with adhesive, in order to hold the components of the dressing together. The adhesive coating will however, decrease the permeability of the film significantly.
Alternatively, the dressing may be produced by combining the layers of the dressing by lamination. However, the heat and pressure of the lamination process may change the permeability properties of the backing layer, as well as the structure of the absorbent layer may be crushed.
Furthermore, if the layers of the dressing are joined by lamination solely, the edge zone of the dressing may have very little if any absorbent properties, increasing the risk of maceration and leakage of the surrounding skin.
The flexibility of a dressing wherein the layers are tied together by adhesive or lamination may also be reduced. This may give rise to handling problems and leakage when used on curved body parts.
Thus, there is still a need for a non-adhesive flexible, highly absorbent wound dressing being capable of absorbing large amounts of wound exudate without giving rise to maceration.